The present invention relates to an image sensing apparatus for a microscope, which senses and displays an observation image obtained from the microscope.
FIG. 11 is a view showing the schematic structure of a conventional image sensing apparatus for a general microscope. FIG. 12 is a schematic view showing color balance adjustment for an image in transmission bright-field observation by this apparatus.
In FIG. 11, an image sensing apparatus 101 is attached to the observation optical system of a microscope 100, and senses an observation image of a specimen enlarged by the microscope 100. The image sensing apparatus 101 performs photoelectric conversion and the like for the observation image, and displays the observation image data on a display unit 102.
Color balance is generally uniformly adjusted for the entire region of observation image data. For example, the ratio of R (Red), G (Green), and B (Blue) in observation image data is uniformly changed over the entire display region.
When a specimen is observed through the microscope, various microscopy techniques such as transmission bright-field observation and fluorescent observation are selected in accordance with the observation purpose for that specimen. However, upon switching the microscopy technique color balance is not adjusted in consideration of the switched microscopy technique. For example, originally color balance needs to be adjusted only for the stained portion of an observation specimen L in an image in transmission bright-field observation like the one shown in FIG. 12. However, color balance is uniformly adjusted for the entire region of observation image data. As a result, an achromatic background portion M, which need not be colored, is undesirably colored to degrade the image quality.
Correcting observation image data later by image software or the like takes a long time. In addition, the operator must execute an extra operation such as designation of a region subjected to color balance adjustment. This demands an extra labor from the operator.
When a specimen is to be observed through a microscope, the specimen surface is irradiated with a quantity of light appropriate for observation in accordance with the observation conditions of the specimen. At this time, the color temperature of the light source changes depending on adjusting (dimming) of illumination light which irradiates the specimen surface. Hence, to obtain a high-quality color image when an observation image is sensed through the microscope by the image sensing apparatus, white balance must be corrected for the sensed image so as to make the white balance uniform regardless of changes in color temperature of the light source adjusted (dimmed) in accordance with observation conditions.
A known example of a conventional white balance correction method is automatically tracking white balance correction in which color balance prepared by averaging the entire display is corrected to always make it white.
According to another white balance correction, when the color temperature changes with insertion/removal of a filter or changes in light quantity of light source, the stage of the microscope is operated to remove the specimen from the image sensing field, and the entire display is made white. In this state, white balance correction is set. While this white balance correction value is held until next new setting, the observation image is sensed.
However, in the method of setting white balance correction while making the entire display white, the microscope must be operated not to display any specimen image on the display in order to make the entire display white every time the color temperature of the light source changes with insertion/removal of a filter or light adjusting (dimming). This greatly degrades the operator's operability.
This white balance correction assumes that a chromatic signal obtained by averaging the colors of the entire display like a natural image is equivalent to a chromatic signal obtained when the entire display is white. That is, an observation image must contain respective colors on average. However, an observation image in microscopic observation ordinarily contains many magenta components or blue components depending on the specimen to be observed. In many cases, a specimen containing many components of a single color is observed. For example, when a specimen containing many magenta components is to be sensed, white balance correction cancels magenta. Then, the specimen portion fades, and the originally white portion is colored in green.
Still another white balance correction method is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-237679. This method adopts a mode in which white balance is corrected automatically following changes in light source or object, and a mode in which white balance is corrected in response to a trigger signal and the current white balance correction state is held until a next trigger is input. In each mode, the white balance correction range is defined by controlling the gains of R and B signals, and white balance is corrected within only this range.
In white balance correction disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-237679, unnatural fading and coloring by white balance correction can be reduced by defining the gain adjustment range for performing correction. However, the above-described problems still arise in an object containing many components of a single color, like a specimen in microscopic observation.